Synthesis and photophysical properties of bis-cyclometallated Iridium(III)-Styryl complexes and their saturated analogues

This manuscript reports the synthesis and photophysical investigation of a series of Ir-III complexes Ir(C boolean AND N)(2)(O boolean AND O) which are functionalized in the para position of the pyridine ring by styryl groups substituted with electron-donor and -acceptor end groups. The saturated derivative Ir(C boolean AND N-ppy-4CH(2)CH(2)C(6)H(4)OMe)(2)(O boolean AND-acac) (4a-H-2) was formed from [Ir(C boolean AND N-ppy-4-CH=CHC6H4OMe)(2)](2)(mu-Cl)(2) (3a) at 140 degrees C, whereas at 80 degrees C the parent unsaturated complexes Ir(C boolean AND N-ppy-4-CH=CHC6H4R)(2)(O boolean AND O) [O boolean AND O = acac, R = OMe (4a), NEt2 (4b), H (4c), NO2 (4d); O boolean AND O = dpm, R = OMe (5a), NEt2 (5b)] were isolated. The saturated complex 4a-H-2 exhibits intense green emission with a 36 % quantum yield at 298 K. The styryl complexes 4a-4d, 5a and 5b are very weakly emissive at 298 K, but show intense red luminescence in alcohol glass at 77 K. The amino- and nitro-substituted complexes 4b and 4d give low-energy emission (lambda(em) = 651 and 647 nm, respectively). The emissive states of these complexes are believed to possess predominant triplet intra-ligand charge-transfer ((ILCT)-I-3) and metal-to-ligand charge-transfer ((MLCT)-M-3) character, respectively. (c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007.